<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="ln"></div>
    <script src="./src/react.js"></script>
    <script src="./src/react-dom.js"></script>
    <script src="./src/babel.js"></script>
    <script type="text/babel">
        class Bdan extends React.Component {
            constructor() {
                super();
                this.user = React.createRef()
            }
            add = () => {
                console.log(document.getElementById("username").value);
            }
            render() {
                return (
                    <div>
                        <input type="text" defaultValue="aa" id="username" ref={this.user} />
                        <input type="button" value="提交" onClick={this.add} />
                    </div>
                )
            }
        }
        ReactDOM.render(
            <Bdan></Bdan>,
            document.getElementById('ln')
        )
    </script>
</body>

</html>